1. Field of the Invention
The present invention relates generally to tubular prostheses, such as grafts, stents, stentgrafts, and the like. More particularly, the present invention provides endoluminal prostheses having improved position indicating,elements which facilitate orienting and deploying of the prostheses within body lumens, particularly within branching blood vessels for the treatment of abdominal and other aneurysms.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition, which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending into one or both of the iliac arteries.
Aortic aneurysms are most commonly treated in open surgical procedures, where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of a usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and requires experienced surgeons and well equipped surgical facilities. Even with the best surgeons and equipment, however, patients being treated frequently are elderly and weakened from cardiovascular and other diseases, reducing the number of eligible patients. Even for eligible patients prior to rupture, conventional aneurysm repair has a relatively high mortality rate. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery takes several weeks, and often requires a lengthy hospital stay.
In order to overcome some or all of these drawbacks, endovascular prosthesis placement for the treatment of aneurysms has been proposed. Although very promising, many of the proposed methods and apparatus suffer from undesirable limitations. In particular, proper positioning of an endovascular prosthesis within the vascular system can be problematic.
Accurately positioning and orienting endoluminal prostheses is critical to the efficacy of endovascular aneurysm therapies. These tubular prostheses are generally introduced into the vascular system within a catheter and in a radially compressed configuration, typically being maneuvered into position under fluoroscopy. The positioned prosthesis will radially expand, preferably engaging and sealing against the endolithium of the healthy vessel wall both upstream and downstream of the weakened, distended aneurysm. The prosthesis may expand resiliently when released from the catheter, or may be mechanically expanded, typically using a balloon catheter. In either case, the prosthesis will preferably span the entire aneurysm to prevent pressure from acting on the weakened luminal wall, and to prevent leakage through any rupture of the aneurysm. To provide these advantages, the prosthesis should be axially positioned accurately across the aneurysm so as to isolate the aneurysm from the blood flow through the prosthetic lumen.
Proper radial orientation of endoluminal prostheses is also important, particularly when deploying branching and asymmetric prostheses within the tortuous vascular system. If the branches of branching prostheses are not oriented toward their respective branching body lumens, the surrounding body lumen may be distended to adapt to the misaligned prosthesis, or the prosthetic lumen may be distorted or even closed entirely. For example, if the trunk of a bifurcated prosthesis is deployed with a branch oriented 90xc2x0 from the iliac arteries (i.e., angling dorsally rather than laterally), the prosthetic branch lumen may fold or kink, and will have to at least bend at a sharp angle to enter the laterally oriented iliac. In fact, as branching prostheses are often assembled in situ, it may not be possible to introduce the branch prosthesis into such a misaligned branch port. As recapture or repositioning of expanded endoluminal prostheses is often problematic, it may even be necessary to resort to an emergency invasive procedure to remedy such misalignment.
Tubular endovascular prostheses are often formed as stent-grafts having a flexible tubular liner or xe2x80x9cgraftxe2x80x9d which is supported by a perforate tubular frame or xe2x80x9cstentxe2x80x9d. The frame perforations define radially expandable structures, while the frame often include metals which are, to some extent, visible under fluoroscopy. To facilitate positioning of endovascular prostheses, it has previously been proposed to coil gold or platinum wires around an element of the perforate frame structure to enhance the visibility of the prosthesis under fluoroscopy. Similarly, it has been suggested that a tube be crimped over an element of the frame. Unfortunately, affixing such structures to the frame may limit or interfere with the radial compressibility of the prosthesis. It can also be difficult to identify the portion of the frame having an enhanced image against the backdrop of the frame itself, and to orient the prosthesis properly based on one or more enhanced frame arms. In one very important improvement, U.S. Pat. No. 5,824,042, herein incorporated by reference for all purposes, describes a radiopaque marker having a passage therethrough to facilitate stitching the marker directly to the liner, which overcomes some of the drawbacks suggested above. Unfortunately, attachments of these sutured markers is somewhat expensive.
Alternatively, it has also been suggested to affix radiopaque lines or image markers to bifurcated grafts in the form of fine wire or chain, either woven into the cloth or applied after weaving, or as an inert paint or plastic. However, the liners of endoluminal prostheses should remain highly flexible, typically being folded when the prosthesis is compressed and unfolding during deployment. Wires, chains, or paints which are sufficiently flexible will generally provide only limited-contrast images when the graft is supported by the obscuring frame, and may become detached from the prosthesis once deployed in the body lumen. Moreover, imaging of such thin, flexible, low-contrast markers is particularly difficult when the prosthesis is in the high density, radially compressed configuration and disposed within a catheter, as is generally required for intravascular maneuvering.
For these reasons, it would be desirable to provide improved endoluminal prostheses and methods for their use. It would be particularly desirable to provide endoluminal prostheses having high-contrast orientation indicating imaging markers which do not interfere with radial compression or expansion, and which are securely and reliably attached to the prosthesis without using sutures, adhesives, and/or weaves. It would further be desirable if such markers could clearly indicate both the position and orientation of the prosthesis, ideally while the prosthesis remains compressed in the delivery catheter, but without substantially increasing the size of the delivery system and/or incurring the high costs of known marker attachment techniques.
2. Description of the Background Art
U.S. Pat. No. 5,824,037, the full disclosure of which is hereby incorporated by reference, describes modular prostheses and prosthetic construction methods. Application Ser. No. 08/104,960, filed Aug. 29, 1996 (Attorney-Docket No. 16380-003410), also incorporated herein by reference, describes bifurcated modular prosthetic structures and in situ methods for their assembly.
Published PCT patent application WO 95/21,592 describes a bifurcated endoluminal prosthesis including a bifurcated stent and a second stent. U.S. Pat. No. 5,387,235 describes a bifurcated graft having radiopaque lines and markers. U.S. Pat. No. 5,776,180 describes stents which include fabric coverings and radiopaque markers formed of wire crimped on the end of a stent or a tube disposed around a length of a wire on the stent.
The present invention provides improved endoluminal prostheses (and methods for their use) having discrete position indicating elements which facilitate the orienting and deploying of the prostheses within body lumens. More specifically, the endoluminal prostheses includes endovascular prostheses, often formed as stent-grafts, having an improved radiopaque image marker to be applied to the graft before the graft is deployed. Typically, the marker is in the form of a flat metal plate resembling a circular disk or xe2x80x9cbutton,xe2x80x9d however, the shape of the plate may be modified as desired to conform to the needs of the application. The plate may be fastened or secured on to the graft at any desired position using a pair of fastening shanks or tangs which extend parallel to each other outward from a major surface of the plate, in a fashion similar to the fastening shanks of a common staple. The marker, herein referred to as a xe2x80x9cstaplebuttonxe2x80x9d marker, is operated by forcing the fastening shanks through the graft liner, until an underside of the button rests on the liner. Each shank is then folded down on the other side of the liner, so as to bind the material between the folded fastening shanks and the button.
The staplebutton thus described provides a high-contrast, orientation indicating imaging marker, which does not interfere with radial compression or expansion of an endoluminal prostheses on which it is being used. By using fastening shanks or tangs, the staplebutton can be securely and reliably attached to the liner or any other portion of the prosthesis without fear of the inadvertent detachment of the marker. One other advantage of the liner supported marker element is that the marker element can move out of the way of the frame with the liner when the prosthesis is compressed and further, it remains out of the way when the liner (and frame) is deployed. The staplebutton marker can also clearly indicate both the position and orientation of the prosthesis, while the prosthesis remains compressed in the delivery catheter, but without substantially increasing the size of the delivery system.
In a first aspect, the present invention provides a tubular graft comprising a polyester fabric and an imagable body disposed on the liner. The body includes a plate and at least two shanks integral with the plate, the shanks affixing the imagable body on the liner. The imagable body provides a sharp contrast so as to indicate the liner position when the prosthesis is imaged within the patient body.
In a preferred aspect, the present invention provides an endoluminal prosthesis for deployment in a body lumen of a patient body. The prosthesis includes a tubular fabric liner having a proximal end, a distal end, and a lumen therebetween. A plurality of imagable bodies are attached to the liner and provide a sharp contrast so as to define a pattern which indicates the prosthesis position when the prosthesis is imaged within the patient body. Each imagable body has a plate and two integral fastening members, which facilitate the attachment of the imagable bodies to the liner.
In another aspect, the present invention provides an endoluminal prosthesis for deployment in a body lumen of a patient body. The prosthesis includes a tubular fabric liner having a proximal end, a distal end, and a lumen therebetween and a radially expandable frame which supports the liner. A plurality of radiopaque marker elements are disposed on the liner. Each marker includes a plate having a first and a second opposed major surface and two fastening members which extend from the second major surface, through the line, and along the plate so that the marker elements are attached to the liner. The marker elements indicate a position of the prosthesis when the prosthesis is imaged within the body lumen.
Advantageously, the imagable bodies described above can be aligned with openings of a perforate frame structure used to support the fabric liner so that at least some of the imagable bodies are visible through the associated openings when the frame is expanded. Advantageously, the markers need not actually be attached to the frame directly. Such imagable bodies are clearly visible when the prosthesis is deployed, and can also be sized to produce distinct images even when the frame is compressed within a delivery catheter, but should not interfere with the radial expansion of the frame during deployment. The imagable bodies optionally comprise a radiopaque material, or may alternatively produce enhanced ultrasound images.